Albert l



A. L. HARVEY. CONTROL SYSTEM.

APPLICATION FILED MAY 12. I9 I9.

1 ,425,646. Patent d Aug. 15, 1 922.

INVENTOR A/berf Lf/arvey 14 BY A ATTORNEY Uurr s'rAres PATENT OFFICE,

ALBERT' 1t. ,HARVEY, or WILKINSBURG, PENNSYLVANIA, ASS1ZGNOR 'ro WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY,

VANIA.

A CORPORATION OF PENNSYL- CONTROL SYSTEM.

To all whom it away cancer n Be it known that l, ALBERT L. HARVEY, a

. citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Control Systems, of which the following is a specification. 1

My invention relates to motor-control sys terns and particularly to systems for control: ling the acceleration and the deceleration 0t direct-current motors.

The object of-my ih-ention is to provide a new and improved system for controlling the field excitation of hunt and compound= wound motors during acceleration-and deceleration.

The resist-or, which is connected in C11- cuit with the shunt field-magnet winding, is normally short-circuited by a relay that is biased to closed position and may be opened upon the counter-electroinotive force of the motor attaining a predetermined value. The resistor is thus inserted into circuit independently of the condition 01 the load nof any condition other than the motor speed. If the motor is provided with means for dynamic-braking, the relay will provide for strengthening the field when it is reclosed upon the counter-electromotive, force of the motor falling to a predetermined value, so

' that the dynamic-braking current may be maintained more nearly constant. If dynamic-braking is not employed, the field winding and the relay coil may'be permanentl y connected to the line, thus providing for a strongly excited field-magnet winding during the accelerating period but for a weakly excited winding at all other times.

My invention will be made clear in connection with the accompanying drawings in which Figure l is a' diagrammatic view of circuits and apparatus embodying my in vention asapplied to a motor. that is provided with means for dynamic-braking. Fig. 2 is a diagrammatic View 01 a modification.

In Fi '1 a motor havin I an armature 1 and a. shunt field-magnet wirulingrQ, is connectcd towline conductors 3 and 1 by a line contactor 5 having an cnergizingicoil' (h-tho circuit of which isun'der the control of a master switch 7. resistor normally connected in series with the, arn'iatme 1, a

dynamic-braking resistor 9 is adapted to be electromotive force increases, in c losed by the coils 17 andlS, respectively;

:16 will remain open.

1919. Serial No. 296,563.

connected in circuit with the armature 1,

Specification of Letters Patent. Patented Aug. 15,1922.

during dynamic-braking, and a resistor 10- is connected in circuit with the shunt field magnet winding 2, though short-circuited therefrom by a relay or re: lays 11 and 12, two being shown in this instance for purposes of illustration, respectively, coils 13 and 14 that are connected across the terminals of the armature 1.

The'coils 13 and 1 1 may have difi'erent it is normally having,

numbers of ampere turns,'in order to effect the operation of the relays 11 and 12 at different values of the counter-electromotive force of the motor or the other ways, be adapted to respond at different times. 1 The resistor 8 is adapted to be short-.circuited by a contactor or contactors 15and l6having actuating coils 17 and 18, respectively, that, for purposes of illustration, are shown as connected across the motor armature in circuit with Contact memrelays may, in

hers under the control of the master switch 7 The line contactor 5 is adapted to, occupy two positions in one of which it closes the motor circuit and in the other of which it establishes a dynamic-braking circuit, the line contactor being adapted to be maintained in the latter-named position by a coil19 which is energized by the current traversing the dynamic-braking circuit,

In the first position of the master switch 7, the circuit of the coil 6 is closed to establish the circuit of the" motor, which extends from the line conductor 3, through the line cont-actor 5, the armature 1 and the resistor. 8' to the line conductor 4; The shunt fieldmagnet winding 2 is, of course, connected in parallel to the armature 1 and the fsistor 8, the-adjustable resistor 1Q being 'at this time, short-circuited by the relays tf'and 12. As the motor accelerates and it V counter.

dhsequence, the contactors 15 and 16 are c which are energized in accordance with thecdunter-electromotive force of the motor, if the master switch 7 occupies its second or its third position. So long. asthemaster switch 7 00-; cupies its first position the oontactors 15-and Upon the open ng oftherelay 11, ail-portion 1, 10 l Q incense of the'adjustable resistor 10 is inserted into the circuit of the shunt field-magnet winding 2 and, upon the opening of the relay 12, the remainder of this resistor is inserted into circuit, whereby the motor speed may be in or ,ased to any desired value. The speed of as motor may thus be controlled by means of the contactors l5 and 16,- which are under the control. of the master switch 7, and/ the relays 11 and 12 which control the adjustable resistor 10.

When it'is desired to stop the motor, the master switch *Fmay be actuated to its illus-- trated or oil )osition, thereby breaking the circuits of the coils 6, l7 and 18. The line contactor 5 is thereupon opened by gravity andthe dynamicbraking circuit is established from one terminal of the armature 1 .through the coil 19, the line contactor 5 andthe dynamic-braking resistor 9, to the; otherterminal of the armature 1. During the early part of the v dynamic-b-raking period the coils 13 and I l will be si'ii'liciently energized to maintain the relays ll and i2 open, so thatfthe field-magnet Winding will be weakly excited. As; the motor continues todccelerate, however, the coils l3 and 1% become energized by a weaker cur rent so that, ultimately, the relays l2 and 11 will close in the order named, which is the reverse order of that in which they opened during acceleration, thereby providingfor successively strengthening the excitation of the field-magnet winding 2, so that a successively stronger field is provided for the motor during the dynamic-braking period, whereby the dynamic-braking" cur rent may be maintained more nearly uniform.

In Fig; 2, I have shown a. control system for a motor that is not provided with n'icans for dynamic-brakin In order to si'n'ipliiy the drawing, 1 have shown but one relay 11, though additional relays may be employed, if desired, as in Fig. l. The shunt fieldmagnet winding 2 and the coil l3 connected, in this instance, not directly to the leftdiand terminal of the armature i, but directly to the line conductor 3, which is separated" from the left-hand terminal of the armature 1 by the contactor 5. The, shunt field-magnet winding '2 and the coil 13 are thus normally energized by line voltage, irrespective of the position which the contactor may happen to occupy. relay '11. is tli'i'is normally maintained open by its actuating coil 13, so that the shunt field-magnet winding 2 is normally weakly excited. i

Upon the closing of the line contactor 5, in response to the actuation of the master switch 7, the armature circuit iscstalilishcd, whereupon the coil 1.3 becomes, in cil'cct, short-circuited, so that the relay ll is closed by gravity to effect the short-circuiting of The I the resistor 10. The conditions are then similar to those obtaining at the time of the closing of the contactor 5 in the-system of Fig. l, and the inotor'commences to accelerate in a fashion similar to that above de scribed. Upon the counter-electromotive force of the motor reaching a predetermined value, the relay 11 is opened by the coil 13 a ,resistor in series therewith, of a dynamic.

braking resistor and a switchbiased to its closed position to eilect the shunting of said field resistor, said switch having an actuating coil encrg'ized' in accordance with the counter-electronictive force of said motor to control a shunt circuit for said resistor during acceleration and during dynamic braking of'said motor.

2. The; combination with an electric motor having a shunt field-magnet winding-and a resistor-in. circuit therewith, of a dynamic-- braking circuit for said motor and means for rendering; said field resistor effective or ineffective according as the counter-electromotive force of said motor exceeds or fallsbelow a undetermined value during acceleration and durin dynamic braking of said motor.

3; 'l heci'mibination with an electric motor having; an armature, a dynamic-braking resistor associated therewith, and a shunt fieldmagnet winding: having a resistor in series therewith, of a switch biased to closed position to effect the short-circuiting of said field resistor and having a coil connected across said armature for opening said switch to insert said field resistor into circuit;

4. The combination with an electric nlotor having an armature. and a shunt field-mall:- net winding, a d ynamic-l'irahing rcsistcr.

and a resistor in circuit with said field-magnet winding, of means for rendering said resistor effective during acceleration of said motor when the connter-clcctromotive Force of said motor exceeds a predetermined value and for gradually rendering said resistor inctl'ective during; dynamic braking oi said motor when the counter-clcctromotive force of the motor falls to predetermined values.

5. The combi-nationwith an electric motor having a shunt fieldanagnet winding and a resistor therefor, of a dynamicdirahing rcsistor, and means for coni'icctingz the field resistor in time, during acceleration and ing the field resistor to accelerate the motor I I and for gradually shunting said field re sistor during dynamic braking.

In testimony whereof, I have hereunto;

subscribed my name this 30th day of Aprii- ALBERT L. 

